Conventionally, as a power transmission device installed in a vehicle or the like, a power transmission system including a transmission which outputs a driving force from an internal combustion engine while performing speed-changing, a differential device which allocates the driving force outputted from the transmission to left and right drive wheels, and a transfer device arranged adjacent to the differential device and allocating the driving force to front and rear drive wheels has been known (see Japanese Patent Application Publication No. 2015-168392, for example).
In a power transmission system of Japanese Patent Application Publication No. 2015-168392, a differential device includes a final driven gear that is rotatably supported by a case of the power transmission device and meshes with a final drive gear.
A known transfer device includes a transfer input gear to which a driving force of the final driven gear of the differential device is transmitted, a transfer input shaft that is rotatably supported by the case of the power transmission device and that supports the transfer input gear, a first bevel gear supported by the transfer input shaft, a second bevel gear that meshes with the first bevel gear, and a transfer output shaft that supports the second bevel gear.
In a transfer device of a conventional power transmission system such as that described in Japanese Patent Application Publication No. 2015-168392, a lubricating fluid such as lubricating oil needs to be supplied to meshing parts of gears located inside of the power transfer system, bearing for pivotally supporting a shaft in a rotatable manner, and other parts.
Conceivable methods of supplying a lubricating fluid to the inside of the transfer device include installation of a lubrication mechanism of lubricating fluid in the transfer device, for example. It is also conceivable to feed lubricating oil scraped or scooped up by a final driven gear from an oil reservoir inside a first case of the differential device, through a channel formed in the first case and a second case, from the differential device to the transfer device.
However, these methods require a space for arranging the lubrication mechanism for the transfer device, or thickness for forming a channel in the first case and the second case. Hence, this may enlarge the system as a whole.
There is a need of providing a power transmission system that can supply a sufficient amount of lubricating fluid to a transfer device, while suppressing enlargement of the system.